There are two parts to making a character "iconic". Except don't use that word. Ubisoft ruined the word "iconic", and now people use it too liberally. It's not the right word, anyways.
The first part of what makes Poppy DISTINCT is her visual profile. This is their basic outline and color that makes them instantly distinguishable from everyone else, even if you're seeing them in the corner of your eye. It's how you immediately know if you're being ganked by Garen or Jarvan before they start using any of their skills. Poppy's profile is defined largely by her large white twin tails, a small profile overall, and a gold base. And yes, from what I understand they are still using her general appearance (heavily armored yordle girl with a hammer, a shield and twin tails), but updating her to keep in line with the new yordle profile. She will have huge adorable ears just like Heimer, Gnar and Tristana.
Her ROLE in the party is confirmed now to be a tank. Not sure what kind of tank, but they're moving forward with a focus on low health tankiness. I think she might be a disruptor tank, as in she shoves the enemy around like Alistar or the non-grab parts of Thresh, Nautilus and Blitz so they can't focus her allies. Will this mean she can double as a support? I hope so. It means I can play her more often as a support main.